Conventionally, in order to evaluate pathological changes of the urinary tract such as the renal pelvis, ureter, and urinary bladder, an excretory urography examination had been performed using X-ray imaging. However, because the information content of CT (Computer Tomography) scanning is greater than that of X-ray imaging, CT scanning examinations have been increasingly performed these days.
CT Urography is a method to evaluate pathological changes of the urinary tract using CT scanning (see Non-patent Literature 1). As described in Non-patent Literature 1, in CT Urography, scanning is performed immediately after a contrast medium is administered, and then, additionally, scanning is performed again after the contrast medium is excreted into the urinary tract. Therefore, it takes a longer time to scan than normal CT scanning. Thus, a contrast medium is administered, and it takes a longer time to scan, which results in a great burden for an object.
There is a request that urinary tract extraction is performed for data scanned without a contrast medium by image processing to display a three-dimensional image of the urinary tract. Region growing processing (Region Growing) is well known as organ extraction processing to display certain organs three-dimensionally (see Patent Literature 1). The method described in PTL 1 has achieved highly reliable region extraction by combining and using a condition in light of a local concentration change and a condition in light of a global concentration change as a growing condition in region growing processing.